Azacitidine front-line in 339 patients with myelodysplastic syndromes and acute myeloid leukaemia: comparison of French-American-British and World Health Organization classifications

BACKGROUND: The MDS-IWG and NCCN currently endorse both FAB and WHO classifications of MDS and AML, thus allowing patients with 20–30 % bone marrow blasts (AML20–30, formerly MDS-RAEB-t) to be categorised and treated as either MDS or AML. In addition, an artificial distinction between AML20–30 and AML30+ was made by regulatory agencies by initially restricting approval of azacitidine to AML20–30. Thus, uncertainty prevails regarding the diagnosis, prognosis and optimal treatment timing and strategy for patients with AML20–30. Here, we aim to provide clarification for patients treated with azacitidine front-line. METHODS: The Austrian Azacitidine Registry is a multicentre database (ClinicalTrials.gov: NCT01595295). For this analysis, we selected 339 patients treated with azacitidine front-line. According to the WHO classification 53, 96 and 190 patients had MDS-RAEB-I, MDS-RAEB-II and AML (AML20–30: n = 79; AML30+: n = 111), respectively. According to the FAB classification, 131, 101 and 111 patients had MDS-RAEB, MDS-RAEB-t and AML, respectively. RESULTS: The median ages of patients with MDS and AML were 72 (range 37–87) and 77 (range 23–93) years, respectively. Overall, 80 % of classifiable patients (≤30 % bone marrow blasts) had intermediate-2 or high-risk IPSS scores. Most other baseline, treatment and response characteristics were similar between patients diagnosed with MDS or AML. WHO-classified patients with AML20–30 had significantly worse OS than patients with MDS-RAEB-II (13.1 vs 18.9 months; p = 0.010), but similar OS to patients with AML30+ (10.9 vs 13.1 months; p = 0.238). AML patients that showed MDS-related features did not have worse outcomes compared with patients who did not (13.2 vs 8.9 months; p = 0.104). FAB-classified patients with MDS-RAEB-t had similar survival to patients with AML30+ (12.8 vs 10.9 months; p = 0.376), but significantly worse OS than patients with MDS-RAEB (10.9 vs 24.4 months; p < 0.001). CONCLUSIONS: Our data demonstrate the validity of the WHO classification of MDS and AML, and its superiority over the former FAB classification, for patients treated with azacitidine front-line. Neither bone marrow blast count nor presence of MDS-related features had an adverse prognostic impact on survival. Patients with AML20–30 should therefore be regarded as having ‘true AML’ and in our opinion treatment should be initiated without delay. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13045-016-0263-4) contains supplementary material, which is available to authorized users.